/*
** $Id: loadlib.c,v 1.130 2017/01/12 17:14:26 roberto Exp $
** Dynamic library loader for Lua
** See Copyright Notice in lua.h
**
** This module contains an implementation of loadlib for Unix systems
** that have dlfcn, an implementation for Windows, and a stub for other
** systems.
*/

#define loadlib_c
#define LUA_LIB

#include "lprefix.h"


#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "lua.h"

#include "lauxlib.h"
#include "lualib.h"

#ifdef WIN32
#include <direct.h>
#define chdir _chdir
#else
#include <unistd.h>
#define MAX_PATH PATH_MAX
#endif

/*
** LUA_IGMARK is a mark to ignore all before it when building the
** luaopen_ function name.
*/
#if !defined (LUA_IGMARK)
#define LUA_IGMARK      "-"
#endif


/*
** LUA_CSUBSEP is the character that replaces dots in submodule names
** when searching for a C loader.
** LUA_LSUBSEP is the character that replaces dots in submodule names
** when searching for a Lua loader.
*/
#if !defined(LUA_CSUBSEP)
#define LUA_CSUBSEP     LUA_DIRSEP
#endif

#if !defined(LUA_LSUBSEP)
#define LUA_LSUBSEP     LUA_DIRSEP
#endif


/* prefix for open functions in C libraries */
#define LUA_POF     "luaopen_"

/* separator for open functions in C libraries */
#define LUA_OFSEP   "_"


/*
** unique key for table in the registry that keeps handles
** for all loaded C libraries
*/
static const int CLIBS = 0;

#define LIB_FAIL    "open"


#define setprogdir(L)           ((void)0)


/*
** system-dependent functions
*/

/*
** unload library 'lib'
*/
static void lsys_unloadlib( void* lib );

/*
** load C library in file 'path'. If 'seeglb', load with all names in
** the library global.
** Returns the library; in case of error, returns NULL plus an
** error string in the stack.
*/
static void* lsys_load( lua_State* L, const char* path, int seeglb );

/*
** Try to find a function named 'sym' in library 'lib'.
** Returns the function; in case of error, returns NULL plus an
** error string in the stack.
*/
static lua_CFunction lsys_sym( lua_State* L, void* lib, const char* sym );




#if defined(LUA_USE_DLOPEN) /* { */
/*
** {========================================================================
** This is an implementation of loadlib based on the dlfcn interface.
** The dlfcn interface is available in Linux, SunOS, Solaris, IRIX, FreeBSD,
** NetBSD, AIX 4.2, HPUX 11, and  probably most other Unix flavors, at least
** as an emulation layer on top of native functions.
** =========================================================================
*/

#include <dlfcn.h>

/*
** Macro to convert pointer-to-void* to pointer-to-function. This cast
** is undefined according to ISO C, but POSIX assumes that it works.
** (The '__extension__' in gnu compilers is only to avoid warnings.)
*/
#if defined(__GNUC__)
#define cast_func(p) (__extension__ (lua_CFunction)(p))
#else
#define cast_func(p) ((lua_CFunction)(p))
#endif


static void lsys_unloadlib( void* lib ) {
    dlclose( lib );
}


static void* lsys_load( lua_State* L, const char* path, int seeglb ) {
    void* lib = dlopen( path, RTLD_NOW | ( seeglb ? RTLD_GLOBAL : RTLD_LOCAL ) );

    if ( lib == NULL ) {
        lua_pushstring( L, dlerror() );
    }

    return lib;
}


static lua_CFunction lsys_sym( lua_State* L, void* lib, const char* sym ) {
    lua_CFunction f = cast_func( dlsym( lib, sym ) );

    if ( f == NULL ) {
        lua_pushstring( L, dlerror() );
    }

    return f;
}

/* }====================================================== */



#elif defined(LUA_DL_DLL)   /* }{ */
/*
** {======================================================================
** This is an implementation of loadlib for Windows using native functions.
** =======================================================================
*/

#include <windows.h>


/*
** optional flags for LoadLibraryEx
*/
#if !defined(LUA_LLE_FLAGS)
#define LUA_LLE_FLAGS   0
#endif


#undef setprogdir


/*
** Replace in the path (on the top of the stack) any occurrence
** of LUA_EXEC_DIR with the executable's path.
*/
static void setprogdir( lua_State* L ) {
    char buff[MAX_PATH + 1];
    char* lb;
    DWORD nsize = sizeof( buff ) / sizeof( char );
    DWORD n = GetModuleFileNameA( NULL, buff, nsize ); /* get exec. name */

    if ( n == 0 || n == nsize || ( lb = strrchr( buff, '\\' ) ) == NULL ) {
        luaL_error( L, "unable to get ModuleFileName" );
    }
    else {
        *lb = '\0';  /* cut name on the last '\\' to get the path */
        luaL_gsub( L, lua_tostring( L, -1 ), LUA_EXEC_DIR, buff );
        lua_remove( L, -2 ); /* remove original string */
    }
}




static void pusherror( lua_State* L ) {
    int error = GetLastError();
    char buffer[128];

    if ( FormatMessageA( FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_FROM_SYSTEM,
                         NULL, error, 0, buffer, sizeof( buffer ) / sizeof( char ), NULL ) ) {
        lua_pushstring( L, buffer );
    }
    else {
        lua_pushfstring( L, "system error %d\n", error );
    }
}

static void lsys_unloadlib( void* lib ) {
    FreeLibrary( ( HMODULE )lib );
}


static void* lsys_load( lua_State* L, const char* path, int seeglb ) {
    HMODULE lib = LoadLibraryExA( path, NULL, LUA_LLE_FLAGS );
    ( void )( seeglb ); /* not used: symbols are 'global' by default */

    if ( lib == NULL ) {
        pusherror( L );
    }

    return lib;
}


static lua_CFunction lsys_sym( lua_State* L, void* lib, const char* sym ) {
    lua_CFunction f = ( lua_CFunction )GetProcAddress( ( HMODULE )lib, sym );

    if ( f == NULL ) {
        pusherror( L );
    }

    return f;
}

/* }====================================================== */


#else               /* }{ */
/*
** {======================================================
** Fallback for other systems
** =======================================================
*/

#undef LIB_FAIL
#define LIB_FAIL    "absent"


#define DLMSG   "dynamic libraries not enabled; check your Lua installation"


static void lsys_unloadlib( void* lib ) {
    ( void )( lib ); /* not used */
}


static void* lsys_load( lua_State* L, const char* path, int seeglb ) {
    ( void )( path );
    ( void )( seeglb ); /* not used */
    lua_pushliteral( L, DLMSG );
    return NULL;
}


static lua_CFunction lsys_sym( lua_State* L, void* lib, const char* sym ) {
    ( void )( lib );
    ( void )( sym ); /* not used */
    lua_pushliteral( L, DLMSG );
    return NULL;
}

/* }====================================================== */
#endif              /* } */


/*
** {==================================================================
** Set Paths
** ===================================================================
*/

/*
** LUA_PATH_VAR and LUA_CPATH_VAR are the names of the environment
** variables that Lua check to set its paths.
*/
#if !defined(LUA_PATH_VAR)
#define LUA_PATH_VAR    "LUA_PATH"
#endif

#if !defined(LUA_CPATH_VAR)
#define LUA_CPATH_VAR   "LUA_CPATH"
#endif


#define AUXMARK         "\1"    /* auxiliary mark */


/*
** return registry.LUA_NOENV as a boolean
*/
static int noenv( lua_State* L ) {
    int b;
    lua_getfield( L, LUA_REGISTRYINDEX, "LUA_NOENV" );
    b = lua_toboolean( L, -1 );
    lua_pop( L, 1 ); /* remove value */
    return b;
}


/*
** Set a path
*/
static void setpath( lua_State* L, const char* fieldname,
                     const char* envname,
                     const char* dft ) {
    const char* nver = lua_pushfstring( L, "%s%s", envname, LUA_VERSUFFIX );
    const char* path = getenv( nver ); /* use versioned name */

    if ( path == NULL ) { /* no environment variable? */
        path = getenv( envname );    /* try unversioned name */
    }

    if ( path == NULL || noenv( L ) ) { /* no environment variable? */
        lua_pushstring( L, dft );    /* use default */
    }
    else {
        /* replace ";;" by ";AUXMARK;" and then AUXMARK by default path */
        path = luaL_gsub( L, path, LUA_PATH_SEP LUA_PATH_SEP,
                          LUA_PATH_SEP AUXMARK LUA_PATH_SEP );
        luaL_gsub( L, path, AUXMARK, dft );
        lua_remove( L, -2 ); /* remove result from 1st 'gsub' */
    }

    setprogdir( L );
    lua_setfield( L, -3, fieldname ); /* package[fieldname] = path value */
    lua_pop( L, 1 ); /* pop versioned variable name */
}

/* }================================================================== */


/*
** return registry.CLIBS[path]
*/
static void* checkclib( lua_State* L, const char* path ) {
    void* plib;
    lua_rawgetp( L, LUA_REGISTRYINDEX, &CLIBS );
    lua_getfield( L, -1, path );
    plib = lua_touserdata( L, -1 ); /* plib = CLIBS[path] */
    lua_pop( L, 2 ); /* pop CLIBS table and 'plib' */
    return plib;
}


/*
** registry.CLIBS[path] = plib        -- for queries
** registry.CLIBS[#CLIBS + 1] = plib  -- also keep a list of all libraries
*/
static void addtoclib( lua_State* L, const char* path, void* plib ) {
    lua_rawgetp( L, LUA_REGISTRYINDEX, &CLIBS );
    lua_pushlightuserdata( L, plib );
    lua_pushvalue( L, -1 );
    lua_setfield( L, -3, path ); /* CLIBS[path] = plib */
    lua_rawseti( L, -2, luaL_len( L, -2 ) + 1 ); /* CLIBS[#CLIBS + 1] = plib */
    lua_pop( L, 1 ); /* pop CLIBS table */
}


/*
** __gc tag method for CLIBS table: calls 'lsys_unloadlib' for all lib
** handles in list CLIBS
*/
static int gctm( lua_State* L ) {
    lua_Integer n = luaL_len( L, 1 );

    for ( ; n >= 1; n-- ) { /* for each handle, in reverse order */
        lua_rawgeti( L, 1, n ); /* get handle CLIBS[n] */
        lsys_unloadlib( lua_touserdata( L, -1 ) );
        lua_pop( L, 1 ); /* pop handle */
    }

    return 0;
}



/* error codes for 'lookforfunc' */
#define ERRLIB      1
#define ERRFUNC     2

/*
** Look for a C function named 'sym' in a dynamically loaded library
** 'path'.
** First, check whether the library is already loaded; if not, try
** to load it.
** Then, if 'sym' is '*', return true (as library has been loaded).
** Otherwise, look for symbol 'sym' in the library and push a
** C function with that symbol.
** Return 0 and 'true' or a function in the stack; in case of
** errors, return an error code and an error message in the stack.
*/
static int lookforfunc( lua_State* L, const char* path, const char* sym ) {
    void* reg = checkclib( L, path ); /* check loaded C libraries */

    if ( reg == NULL ) { /* must load library? */
        reg = lsys_load( L, path, *sym == '*' ); /* global symbols if 'sym'=='*' */

        if ( reg == NULL ) {
            return ERRLIB;    /* unable to load library */
        }

        addtoclib( L, path, reg );
    }

    if ( *sym == '*' ) { /* loading only library (no function)? */
        lua_pushboolean( L, 1 ); /* return 'true' */
        return 0;  /* no errors */
    }
    else {
        lua_CFunction f = lsys_sym( L, reg, sym );

        if ( f == NULL ) {
            return ERRFUNC;    /* unable to find function */
        }

        lua_pushcfunction( L, f ); /* else create new function */
        return 0;  /* no errors */
    }
}


static int ll_loadlib( lua_State* L ) {
    const char* path = luaL_checkstring( L, 1 );
    const char* init = luaL_checkstring( L, 2 );
    int stat = lookforfunc( L, path, init );

    if ( stat == 0 ) { /* no errors? */
        return 1;    /* return the loaded function */
    }
    else {  /* error; error message is on stack top */
        lua_pushnil( L );
        lua_insert( L, -2 );
        lua_pushstring( L, ( stat == ERRLIB ) ?  LIB_FAIL : "init" );
        return 3;  /* return nil, error message, and where */
    }
}



/*
** {======================================================
** 'require' function
** =======================================================
*/


static int readable( const char* filename ) {
    FILE* f = fopen( filename, "r" ); /* try to open file */

    if ( f == NULL ) {
        return 0;    /* open failed */
    }

    fclose( f );
    return 1;
}


static const char* pushnexttemplate( lua_State* L, const char* path ) {
    const char* l;

    while ( *path == *LUA_PATH_SEP ) {
        path++;    /* skip separators */
    }

    if ( *path == '\0' ) {
        return NULL;    /* no more templates */
    }

    l = strchr( path, *LUA_PATH_SEP ); /* find next separator */

    if ( l == NULL ) {
        l = path + strlen( path );
    }

    lua_pushlstring( L, path, l - path ); /* template */
    return l;
}


static const char* searchpath( lua_State* L, const char* name,
                               const char* path,
                               const char* sep,
                               const char* dirsep ) {
    luaL_Buffer msg;  /* to build error message */
    luaL_buffinit( L, &msg );

    if ( *sep != '\0' ) { /* non-empty separator? */
        name = luaL_gsub( L, name, sep, dirsep );    /* replace it by 'dirsep' */
    }

    while ( ( path = pushnexttemplate( L, path ) ) != NULL ) {
        const char* filename = luaL_gsub( L, lua_tostring( L, -1 ),
                                          LUA_PATH_MARK, name );
        lua_remove( L, -2 ); /* remove path template */

        if ( readable( filename ) ) { /* does file exist and is readable? */
            return filename;    /* return that file name */
        }

        lua_pushfstring( L, "\n\tno file '%s'", filename );
        lua_remove( L, -2 ); /* remove file name */
        luaL_addvalue( &msg ); /* concatenate error msg. entry */
    }

    luaL_pushresult( &msg ); /* create error message */
    return NULL;  /* not found */
}


static int ll_searchpath( lua_State* L ) {
    const char* f = searchpath( L, luaL_checkstring( L, 1 ),
                                luaL_checkstring( L, 2 ),
                                luaL_optstring( L, 3, "." ),
                                luaL_optstring( L, 4, LUA_DIRSEP ) );

    if ( f != NULL ) {
        return 1;
    }
    else {  /* error message is on top of the stack */
        lua_pushnil( L );
        lua_insert( L, -2 );
        return 2;  /* return nil + error message */
    }
}


static const char* findfile( lua_State* L, const char* name,
                             const char* pname,
                             const char* dirsep ) {
    const char* path;
    lua_getfield( L, lua_upvalueindex( 1 ), pname );
    path = lua_tostring( L, -1 );

    if ( path == NULL ) {
        luaL_error( L, "'package.%s' must be a string", pname );
    }

    return searchpath( L, name, path, ".", dirsep );
}


static int checkload( lua_State* L, int stat, const char* filename ) {
    if ( stat ) { /* module loaded successfully? */
        lua_pushstring( L, filename ); /* will be 2nd argument to module */
        return 2;  /* return open function and file name */
    }
    else
        return luaL_error( L, "error loading module '%s' from file '%s':\n\t%s",
                           lua_tostring( L, 1 ), filename, lua_tostring( L, -1 ) );
}


static int searcher_Lua( lua_State* L ) {
    const char* filename;
    const char* name = luaL_checkstring( L, 1 );
    filename = findfile( L, name, "path", LUA_LSUBSEP );

    if ( filename == NULL ) {
        return 1;    /* module not found in this path */
    }

    return checkload( L, ( luaL_loadfile( L, filename ) == LUA_OK ), filename );
}


/*
** Try to find a load function for module 'modname' at file 'filename'.
** First, change '.' to '_' in 'modname'; then, if 'modname' has
** the form X-Y (that is, it has an "ignore mark"), build a function
** name "luaopen_X" and look for it. (For compatibility, if that
** fails, it also tries "luaopen_Y".) If there is no ignore mark,
** look for a function named "luaopen_modname".
*/
static int loadfunc( lua_State* L, const char* filename, const char* modname ) {
    const char* openfunc;
    const char* mark;
    modname = luaL_gsub( L, modname, ".", LUA_OFSEP );
    mark = strchr( modname, *LUA_IGMARK );

    if ( mark ) {
        int stat;
        openfunc = lua_pushlstring( L, modname, mark - modname );
        openfunc = lua_pushfstring( L, LUA_POF"%s", openfunc );
        stat = lookforfunc( L, filename, openfunc );

        if ( stat != ERRFUNC ) {
            return stat;
        }

        modname = mark + 1;  /* else go ahead and try old-style name */
    }

    openfunc = lua_pushfstring( L, LUA_POF"%s", modname );
    return lookforfunc( L, filename, openfunc );
}


static int searcher_C( lua_State* L ) {
    const char* name = luaL_checkstring( L, 1 );
    const char* filename = findfile( L, name, "cpath", LUA_CSUBSEP );

    if ( filename == NULL ) {
        return 1;    /* module not found in this path */
    }

    return checkload( L, ( loadfunc( L, filename, name ) == 0 ), filename );
}


static int searcher_Croot( lua_State* L ) {
    const char* filename;
    const char* name = luaL_checkstring( L, 1 );
    const char* p = strchr( name, '.' );
    int stat;

    if ( p == NULL ) {
        return 0;    /* is root */
    }

    lua_pushlstring( L, name, p - name );
    filename = findfile( L, lua_tostring( L, -1 ), "cpath", LUA_CSUBSEP );

    if ( filename == NULL ) {
        return 1;    /* root not found */
    }

    if ( ( stat = loadfunc( L, filename, name ) ) != 0 ) {
        if ( stat != ERRFUNC ) {
            return checkload( L, 0, filename );    /* real error */
        }
        else {  /* open function not found */
            lua_pushfstring( L, "\n\tno module '%s' in file '%s'", name, filename );
            return 1;
        }
    }

    lua_pushstring( L, filename ); /* will be 2nd argument to module */
    return 2;
}


static int searcher_preload( lua_State* L ) {
    const char* name = luaL_checkstring( L, 1 );
    lua_getfield( L, LUA_REGISTRYINDEX, LUA_PRELOAD_TABLE );

    if ( lua_getfield( L, -1, name ) == LUA_TNIL ) { /* not found? */
        lua_pushfstring( L, "\n\tno field package.preload['%s']", name );
    }

    return 1;
}


static void findloader( lua_State* L, const char* name ) {
    int i;
    luaL_Buffer msg;  /* to build error message */
    luaL_buffinit( L, &msg );

    /* push 'package.searchers' to index 3 in the stack */
    if ( lua_getfield( L, lua_upvalueindex( 1 ), "searchers" ) != LUA_TTABLE ) {
        luaL_error( L, "'package.searchers' must be a table" );
    }

    /*  iterate over available searchers to find a loader */
    for ( i = 1; ; i++ ) {
        if ( lua_rawgeti( L, 3, i ) == LUA_TNIL ) { /* no more searchers? */
            lua_pop( L, 1 ); /* remove nil */
            luaL_pushresult( &msg ); /* create error message */
            luaL_error( L, "module '%s' not found:%s", name, lua_tostring( L, -1 ) );
        }

        lua_pushstring( L, name );
        lua_call( L, 1, 2 ); /* call it */

        if ( lua_isfunction( L, -2 ) ) { /* did it find a loader? */
            return;    /* module loader found */
        }
        else if ( lua_isstring( L, -2 ) ) { /* searcher returned error message? */
            lua_pop( L, 1 ); /* remove extra return */
            luaL_addvalue( &msg ); /* concatenate error message */
        }
        else {
            lua_pop( L, 2 );    /* remove both returns */
        }
    }
}


static int ll_require( lua_State* L ) {
    const char* name = luaL_checkstring( L, 1 );
    lua_settop( L, 1 ); /* LOADED table will be at index 2 */
    lua_getfield( L, LUA_REGISTRYINDEX, LUA_LOADED_TABLE );
    lua_getfield( L, 2, name ); /* LOADED[name] */

    if ( lua_toboolean( L, -1 ) ) { /* is it there? */
        return 1;    /* package is already loaded */
    }

    /* else must load package */
    lua_pop( L, 1 ); /* remove 'getfield' result */
    findloader( L, name );
    lua_pushstring( L, name ); /* pass name as argument to module loader */
    lua_insert( L, -2 ); /* name is 1st argument (before search data) */
    lua_call( L, 2, 1 ); /* run loader to load module */

    if ( !lua_isnil( L, -1 ) ) { /* non-nil return? */
        lua_setfield( L, 2, name );    /* LOADED[name] = returned value */
    }

    if ( lua_getfield( L, 2, name ) == LUA_TNIL ) { /* module set no value? */
        lua_pushboolean( L, 1 ); /* use true as result */
        lua_pushvalue( L, -1 ); /* extra copy to be returned */
        lua_setfield( L, 2, name ); /* LOADED[name] = true */
    }

    return 1;
}

/* }====================================================== */



/*
** {======================================================
** 'module' function
** =======================================================
*/
#if defined(LUA_COMPAT_MODULE)

/*
** changes the environment variable of calling function
*/
static void set_env( lua_State* L ) {
    lua_Debug ar;

    if ( lua_getstack( L, 1, &ar ) == 0 ||
            lua_getinfo( L, "f", &ar ) == 0 || /* get calling function */
            lua_iscfunction( L, -1 ) ) {
        luaL_error( L, "'module' not called from a Lua function" );
    }

    lua_pushvalue( L, -2 ); /* copy new environment table to top */
    lua_setupvalue( L, -2, 1 );
    lua_pop( L, 1 ); /* remove function */
}


static void dooptions( lua_State* L, int n ) {
    int i;

    for ( i = 2; i <= n; i++ ) {
        if ( lua_isfunction( L, i ) ) { /* avoid 'calling' extra info. */
            lua_pushvalue( L, i ); /* get option (a function) */
            lua_pushvalue( L, -2 ); /* module */
            lua_call( L, 1, 0 );
        }
    }
}


static void modinit( lua_State* L, const char* modname ) {
    const char* dot;
    lua_pushvalue( L, -1 );
    lua_setfield( L, -2, "_M" ); /* module._M = module */
    lua_pushstring( L, modname );
    lua_setfield( L, -2, "_NAME" );
    dot = strrchr( modname, '.' ); /* look for last dot in module name */

    if ( dot == NULL ) {
        dot = modname;
    }
    else {
        dot++;
    }

    /* set _PACKAGE as package name (full module name minus last part) */
    lua_pushlstring( L, modname, dot - modname );
    lua_setfield( L, -2, "_PACKAGE" );
}


static int ll_module( lua_State* L ) {
    const char* modname = luaL_checkstring( L, 1 );
    int lastarg = lua_gettop( L ); /* last parameter */
    luaL_pushmodule( L, modname, 1 ); /* get/create module table */

    /* check whether table already has a _NAME field */
    if ( lua_getfield( L, -1, "_NAME" ) != LUA_TNIL ) {
        lua_pop( L, 1 );    /* table is an initialized module */
    }
    else {  /* no; initialize it */
        lua_pop( L, 1 );
        modinit( L, modname );
    }

    lua_pushvalue( L, -1 );
    set_env( L );
    dooptions( L, lastarg );
    return 1;
}


static int ll_seeall( lua_State* L ) {
    luaL_checktype( L, 1, LUA_TTABLE );

    if ( !lua_getmetatable( L, 1 ) ) {
        lua_createtable( L, 0, 1 ); /* create new metatable */
        lua_pushvalue( L, -1 );
        lua_setmetatable( L, 1 );
    }

    lua_pushglobaltable( L );
    lua_setfield( L, -2, "__index" ); /* mt.__index = _G */
    return 0;
}

#endif
/* }====================================================== */



static const luaL_Reg pk_funcs[] = {
    {"loadlib", ll_loadlib},
    {"searchpath", ll_searchpath},
#if defined(LUA_COMPAT_MODULE)
    {"seeall", ll_seeall},
#endif
    /* placeholders */
    {"preload", NULL},
    {"cpath", NULL},
    {"path", NULL},
    {"searchers", NULL},
    {"loaded", NULL},
    {NULL, NULL}
};


static const luaL_Reg ll_funcs[] = {
#if defined(LUA_COMPAT_MODULE)
    {"module", ll_module},
#endif
    {"require", ll_require},
    {NULL, NULL}
};


static void createsearcherstable( lua_State* L ) {
    static const lua_CFunction searchers[] =
    {searcher_preload, searcher_Lua, searcher_C, searcher_Croot, NULL};
    int i;
    /* create 'searchers' table */
    lua_createtable( L, sizeof( searchers ) / sizeof( searchers[0] ) - 1, 0 );

    /* fill it with predefined searchers */
    for ( i = 0; searchers[i] != NULL; i++ ) {
        lua_pushvalue( L, -2 ); /* set 'package' as upvalue for all searchers */
        lua_pushcclosure( L, searchers[i], 1 );
        lua_rawseti( L, -2, i + 1 );
    }

#if defined(LUA_COMPAT_LOADERS)
    lua_pushvalue( L, -1 ); /* make a copy of 'searchers' table */
    lua_setfield( L, -3, "loaders" ); /* put it in field 'loaders' */
#endif
    lua_setfield( L, -2, "searchers" ); /* put it in field 'searchers' */
}


/*
** create table CLIBS to keep track of loaded C libraries,
** setting a finalizer to close all libraries when closing state.
*/
static void createclibstable( lua_State* L ) {
    lua_newtable( L ); /* create CLIBS table */
    lua_createtable( L, 0, 1 ); /* create metatable for CLIBS */
    lua_pushcfunction( L, gctm );
    lua_setfield( L, -2, "__gc" ); /* set finalizer for CLIBS table */
    lua_setmetatable( L, -2 );
    lua_rawsetp( L, LUA_REGISTRYINDEX, &CLIBS ); /* set CLIBS table in registry */
}

static const char* getrootpath(char* path, int len) {
#ifdef WIN32
    GetModuleFileNameA(0, path, len);
    char* p = strrchr(path, '\\');
    *(p+1) = '\0';
    return path;
#elif __APPLE__

    uint32_t size = len;
    int nRet = _NSGetExecutablePath(path, &size);

    if (nRet != 0) {
        return "./";
    }

    char* p = strrchr(path, '/');
    *(p + 1) = '\0';
    return path;
#else
    int nRet = readlink("/proc/self/exe", path, MAX_PATH);

    if (nRet < 0 || nRet >= MAX_PATH) {
        return "./";
    }

    char* p = strrchr(path, '/');
    *(p + 1) = '\0';
    return path;
#endif
}

LUAMOD_API int luaopen_package( lua_State* L ) {
    // patch exe path search
    char path[2*MAX_PATH + 1];
    char root[MAX_PATH + 1];
    strcpy(path, LUA_PATH_DEFAULT);
    strcat(path, ";");
    getrootpath(root, MAX_PATH);
    chdir(root);
    strcat(path, root);
    strcat(path, "?.lua");
    // patch end
    createclibstable( L );
    luaL_newlib( L, pk_funcs ); /* create 'package' table */
    createsearcherstable( L );
    /* set paths */
    setpath( L, "path", LUA_PATH_VAR, path);
    setpath( L, "cpath", LUA_CPATH_VAR, LUA_CPATH_DEFAULT );
    /* store config information */
    lua_pushliteral( L, LUA_DIRSEP "\n" LUA_PATH_SEP "\n" LUA_PATH_MARK "\n"
                     LUA_EXEC_DIR "\n" LUA_IGMARK "\n" );
    lua_setfield( L, -2, "config" );
    /* set field 'loaded' */
    luaL_getsubtable( L, LUA_REGISTRYINDEX, LUA_LOADED_TABLE );
    lua_setfield( L, -2, "loaded" );
    /* set field 'preload' */
    luaL_getsubtable( L, LUA_REGISTRYINDEX, LUA_PRELOAD_TABLE );
    lua_setfield( L, -2, "preload" );
    lua_pushglobaltable( L );
    lua_pushvalue( L, -2 ); /* set 'package' as upvalue for next lib */
    luaL_setfuncs( L, ll_funcs, 1 ); /* open lib into global table */
    lua_pop( L, 1 ); /* pop global table */
    return 1;  /* return 'package' table */
}

